Powdered pigments with improved rheological properties, processes for their preparation and their use with a content of at least 5% of unsubstituted quinacridone

ABSTRACT

Powdered pigments which contain at least 5% of unsubstituted quinacridone and have improved rheological properties for use in paint systems on an alkyd/melamine, acrylic/melamine, acrylate/isocyanate or polyester/isocyanate basis, both of a conventional nature and also of a modern nature of the &#34;high solids&#34; type, onto which--as appropriate before, during or after finishing--1 to 20% by weight of the active substance of a paint additive, prepared by reacting polyisocyanurates which still carry free isocyanate groups and are based on tolylene diisocyanate, hexamethylene diisocyanate or mixtures thereof, with (1) aliphatic mono- or poly-(hydroxycarboxylic acid) C 1  -C 20  -alkyl esters (degree of polymerization 2-50), (2) polyethylene glycols (molecular weight 500-1,500) and (3) 5- or 6-membered, saturated or unsaturated heterocyclic compounds which contain at least 1 nitrogen atom in the ring and reactive amino or hydroxy-C 1  -C 6  -alkyl groups, until isocyanate groups are no longer detectable, has/have been applied, processes for their preparation and their use for pigmenting polymeric materials and for coloring paint systems.

The invention relates to powdered pigments which are coated with 1-20%by weight of the active substance of an additive of the polyurethaneseries prepared as fully described below and contain at least 5% byweight of unsubstituted quinacridone and have improved rheologicalproperties for pigmenting polymeric materials, in particular theconventional and modern paint systems of the "high solids" type, and tothe process for their preparation.

When organic pigments are dispersed in paint systems, the aim must be toachieve optimum stabilization of the pigment particles with the bindersof the paint system. In addition to the chemical structure and thephysical nature of the pigments, the dispersion method and, inparticular, the type of binder and amount of solvent in the paint systemis decisive for the degree of this stabilization. Inadequatestabilization leads to gloss, viscosity and flocculation problems,alongside deterioration of the coloristic pattern. A number of measuresare known for improving these properties of the pigments, and these alllead to a clear reduction in the problems in conventional paint systems.The following may be mentioned here specifically: preparation withsurface-active agents, such as, for example, resin soaps, alkylphenolpolyglycol ether-sulfonates (German Patent No. 2,152,485) or quaternaryammonium compounds (Patent Application No. P 33 38 806.7); and, in thecase of copper phthalocyanines or quinacridones, the addition of smallamounts of sulfonic acids or sulfonic acid derivatives of the pigment onwhich the system is based. A number of paint additives which are addedduring paint conditioning to improve the rheological properties are alsoknown and in some cases are commercially available.

As a result of new developments in the paint field with the aim ofdrastic reduction in the amount of solvent and a marked reduction in thesize of the binder molecules, such as, for example, in the direction of"TSA-NAD" (thermosetting acrylic non-aqueous dispersion) and "highsolids" (paint systems with a binder content of more than 50% duringprocessing), there are considerable difficulties in achieving perfectstabilization of the pigments in these paint systems. For this reason,special additives have been developed, which either

1. are intended to solve the problem by mutual mechanical dispersionwith the pigments in solvents and subsequent combination with the paint,or

2. are added to the paint/pigment mixture before mechanical dispersion.

U.S. Pat. Nos. 4,029,861, 4,032,698, 4,048,207 and 4,070,388 relate toan example of the first said route. Here, the pigment is subjected topredispersion in the paint solvent with the polymeric active substances,which are dissolved in organic solvents, up to 50% by weight of activesubstance, based on the pigment employed, being used. The pigmentdispersion thus obtained is then added to the paint binder system forpigmenting.

The polymeric materials used for dispersion are prepared by linkingpolymeric structural units of the paint with organic compounds carryingacids, basic or silane end groups via at least bifunctional isocyanatesof the aliphatic and aromatic series. Linking can be effected either byurethane or via urea groupings.

A fair number of wetting and dispersing additives for the second saidroute are known.

In European Published Application No. 0,154,678, addition compoundssuitable as dispersing agents are proposed, which are obtained byreacting polyisocyanates having a mean functionality of 2.5 to 6 withmonohydroxide compounds, reacting the reaction product obtained withcompounds of the formula II

    G--(E).sub.n                                               II

wherein E is --OH, --NH₂ and/or --NHR (R representing an alkyl grouphaving 1 to 4 carbon atoms), n is 2 or 3 and G is an aliphatic,cycloaliphatic and/or aromatic group, and further reaction of thereaction product thus obtained with compounds of the formula III

    Z--Q                                                       III

wherein Q is --OH, --NH₂, --NHR (R representing an alkyl group having 1to 4 carbon atoms) or --SH and Z is a group which contains at least onenitrogen-containing basic group.

Both in the case of the technology from U.S. Pat. Nos. 4,029,861,4,032,698, 4,048,207 and 4,070,388, that is to say, for example,predispersing of the pigments with relatively large quantities of theadditive (up to 50%) followed by addition to the paint system, and inthe case of additives for the second said route, paints were obtainedwhich, depending on the pigment employed and the binder system used,lead to coatings of high gloss and sometimes higher tinctorialstrengths, because of the elimination of flocculation, coupled with goodviscosity properties, and which markedly differ from coatings withoutuse of the additive. This positive effect does not generally apply toall pigments and paint systems or pigment/binder combinations.

Thus, in quite a number of cases no improvement is achieved or acontrary effect is observed.

Furthermore, with these technologies, the nature and amount of theadditive for the particular pigment and binder system must be determinedempirically for these technologies, since an optimum result can beachieved only if the specifically required amount, which can varybetween 5 and 50%, is maintained. This can lead to considerablecoloristic problems, especially in the pigment mixtures which arecustomary in the preparation of colored paints.

However advantageous the effect of the polymeric urethane resins, forexample in the route proposed in European Published Application, No.0,154,678, is for the preparation of paints of high rheological quality,this type of application nevertheless also presents disadvantages inpractice.

The addition of up to 20% of additive during paint conditioning, such asis recommended, for example, in the case of commercially available paintadditives of this type, leads to a marked increase in the solventcontent of the paint system and thus goes against the trend in thelatest devetopment of paint systems, such as drastic reduction in theamount of solvent in the paint.

In addition, some commercially available pigments, as already mentioned,do not respond to these additives, which can lead to trouble, especiallywhen pigment mixtures are used in combination with the additive in thepreparation of the paint. Intolerances with pigments which have alreadybeen surface-treated have also been observed.

The application of these additives to pigments in suspension during orafter the preparation has proved to be a particular problem.

There is therefore the need to develop powdered pigments of a qualitysuch that no further additives are required during paint conditioning toachieve optimum rheological properties, and in particular also in modernpaint systems, such as "TSA-NAD" and "high solids".

It has now been found that it is possible to prepare powdered pigmentswhich contain at least 5% of unsubstituted quinacridone and haveimproved rheological properties for use in plastic compositions, inparticular in conventional paint systems or modern paint systems qf the"high solids" type on an alkyd/melamine, acrylic/melamine,acrylate/isocyanate or polyester/isocyanate basis by coating the basepigments with 1-20% by weight of the active substance of additivesduring finishing of the pigment--as appropriate before, during or afterfinishing--which additives are synthesized from the followingcomponents.

Polyisocyanates which still contain free isocyanate groups, for examplebased on tolylene diisocyanate (such as, for example, ^(R) Desmodur ILfrom Bayer AG) or hexamethylene diisocyanate or mixtures thereof, arereacted with the following compounds in succession or with a mixture ofthem until isocyanate groups are no longer detectable:

1. aliphatic mono- or poly-(hydroxycarboxylic acid) C₁ -C₂₀ -alkylesters (degree of polymerization 2-50), such as, for example, thepolyester from 1 mole of decanol and 7 moles of ε-caprolactone,

2. polyethylene glycols (molecular weight 500-1,500) and

3. 5- or 6-membered saturated or unsaturated heterocyclic compoundswhich have at least one nitrogen atom in the ring system and carry agroup which can react with isocyanates, and can be summarized by thegeneral formula

    H--R.sub.1 --R.sub.2 --R.sub.3                             (I).

In this formula, R₁ represents --O-- or --NH--, R₂ represents analkylene group with 1-6 carbon atoms and R₃ represents a 5- or6-membered, saturated or unsaturated heterocyclic ring system containingnitrogen atoms.

Examples of compounds of the said formula (I) mentioned are1-(2-hydroxyethyl)-pyrrolidine, 2-(1-pyrrollidyl)-ethylamine,1-(2-hydroxyethyl)-piperidine, 2-(1-piperidyl)ethylamine,1-(2-aminopropyl)-piperidine, 4-(2-hydroxyethyl)-morpholine,2-(4-morpholinyl)-ethylamine, 4-(3-aminopropyl)-morpholine,1-(2-hydroxyethyl)-piperazine, 1-(2-aminoethyl)-piperazine,1-(2-hydroxyethyl)-2-alkylimidazolines, 1-(3-aminopropyl)-imidazole,1-(3-hydroxypropyl)-imidazole, (2-aminoethyl)-pyridine,(2-hydroxyethyl)-pyridine, (3-hydroxyproyl)-pyridine,(2-hydroxymethyl)-pyridine and N-methyl-2-hydroxymethyl-piperidine.

The reactions are carried out in a manner known per se, such as, forexample, in U.S. Pat. No. 4,032,698, European Published Application No.0,154,678 or patent application No. P 3,446,084.5. The reactions arecarried out in inert solvents; usually, solvents such as hydrocarbonsand ethyers, esters, ketones and acid amides are used.

When the addition products are used as paint additives in paintconditioning, this type of solvents is highly desirable, since solventsof this type are also present in the paint system.

For use in aqueous systems, this type of solvent is less suitable.

For this application, it is preferable to carry out the reaction in atleast partially water-miscible inert solvents, for example thosementioned in Patent Application No. P 3,446,084.5.

It can also be advantageous to carry out the addition reactions atelevated temperatures and in high concentrations and, after the reactionhas been copleted, to dilute with water-miscible solvents.

The present invention specifically relates to powdered pigments whichcontain at least 5% of unsubstituted quinacridone and have improvedrheological properties for coloring polymeric materials, in particularpaint systems onto which before, during or after finishing 1-20% byweight of the active substance of the additives according to theinvention have been applied, the process for the preparation of thecoated pigments and to their use.

It was not to be expected that the result of the invention can beachieved in the absence of paint binders without using mechanicalshearing forces, as in the case of addition of the additive to thepaint, when the resinous additive is added during the pigmentpreparation, namely before, during or after finishing, in an aqueoussuspension which, in addition to the pigment, still contains at leastpartially water-miscible solvents, but this does not exclude exposure ofthe pigment suspension to shearing forces during preparing--asappropriate before, during or after finishing.

It was furthermore not to be expected that it is possible to achieve thesame maximum effect on application of the urethane resin in the pigmentsuspension--as appropriate before, during or after finishing--sinceresin portions which are not adsorbed onto the pigment surface arepresent, on drying of the pigment powder, as coarser portions which areknown to dissolve only with great difficulty during conditioning of thepaint and would interfere with the desired effect, as in fact occurswith purely mechanical mixtures.

Surprisingly, it has been found that, by suitable coating with theabovementioned additives of the polyurethane series, not onlyrheologically perfect pigments are obtained, but that the quantity ofthe additive can be drastically reduced as compared with the applicationduring paint conditioning.

Thus, for example, in the case of the γ-modification of unsubstitutedquinacridone, a rheologically perfect paint is obtained even whencoating with a low concentration of the active substance of theadditive--as named in Example 1.

If the additive is added during paint conditioning, more than twice theconcentration of the additive must be employed in order to achieve acomparable effect.

Moreover, the pigment coated during the preparation shows a markedlyhigher tinctorial strength.

The advantage of the procedure according to the invention, retaining theoptimum coloristic and rheological effect, is to be seen in the factthat no additional solvent is introduced into the paint system, theamount of additive is drastically reduced, application in aqueous phaseis possible and the active substance is firmly adsorbed on the surfaceof the pigments and cannot interact with other pigments duringconditioning of the paint, and no specks appear in the paint.

The powdered pigments according to the invention, in particularquinacridone pigments, are those which contain at least 5% by weight andup to 100% of unsubstituted linear trans-quinacridone. The pigmentmixtures can be in the form of a mixture or preferably in the form ofmixed crystals.

Preferred pigments of the process according to the invention are the β-and γ-crystal modifications of pure unsubstituted lineartrans-quinacridone, mixtures and mixed crystals of at least 5% ofunsubstituted quinacridone and the following quinacridones ##STR1## R₁=H, alkylC₁ -C₄, Hal, --CONR₇ R₈, alkoxyC₁ -C₄

R₂ =H, alkylC₁ -C₄, Hal, --CONR₇ R₈, alkoxyC₁ -C₄

R₃ =H, alkylC₁ -C₄, Hal, --CONR₇ R₈, alkoxyC₁ -C₄

R₄ =H, alkylC₁ -C₄, Hal, --CONR₇ R₈, alkoxyC₁ -C₄

R₅ =H, alkylC₁ -C₄

R₆ =H, alkylC₁ -C₄

R₇ =H, alkylC₁ -C₁₂

R₈ =H, alkylC₁ -C₃

Very particularly preferred pigments of the process according to theinvention are the β- and γ-modifications of unsubstituted quinacridoneand mixed crystals of 2,9-dimethylquinacridone and unsubstitutedquinacridone.

The most obvious way, of isolating the active substance of the additiveand mixing this in solid form with the base pigment, fails since theactive substance in general cannot be dissolved completely in thecontext of paint preparation. Only a slight effect in the direction ofimprovement in rheology is thus achieved, and the non-dissolved resinconstituents interfere with the coloristic pattern.

Since the abovementioned additives and also the additives proposed, forexample, in European Published Application No. 0,145,678, are present,as a result of the preparation, in solvents which are immiscible or onlypartially miscible with water, the nature and manner of applying theadditives to the pigments is of decisive importance.

Depending on the embodiment, the addition can be made to the aqueouspigment suspension, to the pigment suspension in water/solvent mixturesor to the pigment suspension in solvents--as appropriate before, duringor after pigment finishing.

With some pigments, especially with hiding pigments of high quality, itis thus possible to stir the dissolved additive in the form, in which itis prepared, into the solvent-free base pigment suspension obtainedduring the preparation. When absorption of the additive onto the basepigment has ended, the additive solvent can be removed by distillation.

If the solvent of the additive leads to undesirable coloristic changesto the pigment or to technical difficulties during application to thepigment suspension, it is advantageous to use the additive in a solventwhich is also suitable or used for finishing.

Solvents which are suitable for the process according to the inventionare preferably those which are at least partly water-miscible, such as,for example, aliphatic alcohols with 1-6 carbon atoms, such as, forexample, ethanol, propanol, isobutanol or amyl alcohol; glycols, glycolethers and glycol esters, such as, for example, ethylene glycol,diethylene glycol, propylene glycol, glycol mono-C₁ -C₆ -ethyl (sic)ethers, diglycol mono-C₁ -C₄ -alkyl ethers, diglycol dimethyl ether,ethylglycol acetate, methylglycol acetate and butyldiglycol acetate;ketones of the general formula ##STR2## such as, for example, acetone,methyl ethyl ketone, methyl isobutyl ketone or diacetone alcohol(4-methyl-4-hydroxy-pentan-2-one); aliphatic carboxylic acids with 1-4carbon atoms, such as, for example, formic acid, acetic acid orpropionic acid, aliphatic carboxylic acid amides with 1-5 carbon atoms,such as, for example, dimethylformamide; and cyclic carboxylic acidamides, such as, for example, N-methylpyrrolidone.

The use of the solvents mentioned is advisable, in particular, inconnection with thermal aftertreatment of a pigment--for example toincrease its hiding power or to improve other technological properties.The solvent in which the thermal aftertreatment of the pigment iscarried out is advantageously chosen here. The addition of the additiveor its solution can also be effected here before, during or after thefinishing. The solvent can then be driven off rapidly andquantitatively, for example by steam, and the pigment can then beisolated from the aqueous suspension which remains.

The application of the active substance in one of the solvents mentionedcan also be effected without prior or subsequent thermal treatment(finishing) of the pigment, the solvent used being distilled off again,for example with steam, immediately after addition of the additivesolution to the aqueous pigment suspension, with intensive stirring.

If the additive is not available in such a solvent, the active substanceof the additive should be converted into an appropriate form suitablefor the particular pigment, i.e. the active substance should be isolatedand dissolved in a suitable solvent for the preparation. There arevarious methods for converting the active substance of the additive intoa form suitable for the process according to the invention.

1. To isolate the active substance of the additive, the solvent can bedistilled off under reduced pressure and the active substance whichremains can be dissolved in a solvent suitable for the preparation, suchas, for example, lower aliphatic carboxylic acids, ketones, alcohols oresters.

2. Another very widely applicable preferred method comprises a procedurein which the solvent, in which the additive is dissolved, is distilledoff from the additive, after addition of high-boiling solvents suitablefor the preparation, such as, for example, aliphatic carboxylic acids,glycols or glycol acetates, and the active substance of the additive isthus brought into a dissolved form suitable for use. It is advantageoushere to carry out the distillation under reduced pressure and to distilloff the solvent azeotropically in the presence of small amounts ofwater.

For later use, according to the invention, of the active substance ofthe additive, it is advantageous if the organic solvent in which theactive substance of the additive is dissolved after these measures is atleast partially water-soluble, because the additive can thereby beapplied in a simple manner in aqueous pigment suspensions. The use oforganic carboxylic acids is particularly advisable since the claimedadditives have a weakly basic character. In these cases, it may beadvantageous to neutralize the organic acid or render the pigmentsuspension weakly alkaline after preparation.

It may furthermore be of advantage to neutralize the basic groups of theadditives according to the invention with equivalent amounts of anionicauxiliaries, such as, for example, alkylphenol polyglycolether-sulfates, resin soaps or sulfosuccinic acid esters.

The addition of these auxiliaries can in each case be carried outbefore, during or after finishing. However, it is not necessary to addthe additive and auxiliary in the same stage of pigment finishing.

The powdered pigments prepared according to the invention verysatisfactory rheological properties, such as markedly improved gloss,viscosity and flocculation properties, in all paint systems, but aboveall in the systems which are usually difficult to pigment, such as"TSA-NAD" and "high solids".

The process according to the invention is illustrated in more detail bythe following examples. The parts and percentages mentioned here relateto the weight.

EXAMPLE 1

200 parts of an aqueous pigment suspension with a pigment content of6-7% of the hiding γ-modification of C.I. Pigment Violet 19 (73900),such as is obtained after finishing, are heated to 50° C. in a stirredvessel, with stirring, and 3.5 parts of an additive, the preparation ofwhich is described in Example E, are slowly added at this temperature.After the mixture has been stirred at 50° C. for 3 hours, it is broughtto pH 8 with dilute sodium hydroxide solution and stirred at 50° C. fora further hour. Thereafter, the additive solvent is distilled off withsteam and the pigment is filtered off, washed with water and then dried.The pigment yield is at least 98% of theory. The bluish-tinged redpigment prepared in this manner is the linear transquinacridone in ahighly crystalline γ-modification. It is distinguished by outstandingrheological properties; the full shade paint coatings of high hidingpower produced with it exhibit a fog-free clear color shade and a quiteoutstanding gloss.

For comparison, a pigment was prepared under otherwise identicalconditions, but without the addition of additive.

The comparison coloration is clearly more matt in the full shade paintcoatings with a milky fog, and the viscosity in "high solids" is clearlypoorer. For comparison of the gloss values, the full shade cast films,stoved in an oven, of 7% "TSA-NAD" paints prepared under the sameconditions which, before casting, were brought to a viscosity of 20seconds (measured in a φ 4 mm Ford cup) with paint solvents, weremeasured with a Hunterlab D48D gloss-measuring apparatus under an angleof 20°, the following values being read off:

    ______________________________________                                        Pigment according to Example 1:                                                                     81.5                                                    Comparison example:   31.8                                                    ______________________________________                                    

EXAMPLE 2

If the procedure followed is as described in Example 1, but, instead ofthe additive mentioned there, 3.9 parts of the additive obtainedaccording to Example A are employed and the pigment is then isolatedwithout prior distillation, a comparable result is also obtained. Glossvalue: 80.5.

EXAMPLE 3

500 parts of an aqueous-isobutanolic pigment suspension (isobutanolcontent 20%) with a pigment content of 6.5% of the hiding γ-modificationof C.I. Pigment Violet 19, such as is obtained after finishing, areheated to 50° C., with stirring, and a solution of 6 parts of additivesolution (22%) (prepared according to Example K) and 12 parts of 100%pure isobutanol is added at this temperature in the course of 30minutes. The mixture is then stirred at 50° C. for a further 3 hours andbrought to pH 7.5 with dilute sodium hydroxide solution, and stirring iscontinued at 50° C. for 2 hours. The isobutanol is then distilled offwith steam and the pigment is filtered off, washed with water and driedat 80° C. The bluish-tinged red pigment obtained in a yield of more than98% exhibits a fog-free full shade paint coating of high hiding power,an excellent gloss and an outstanding viscosity in the "TSA-NAD" system.A value of 88.8 was determined in the gloss measurement according toExample 1. In contrast, the non-prepared comparison shows a gloss valueof 31.8.

EXAMPLE 4

(a) 13.6 parts of the additive solution obtained according to Example Iare slowly added to 500 parts of a 6% aqueous suspension of theβ-crystal modification of C.I. Pigment Violet 19 (73900) at 70° C., withstirring. The mixture is then stirred at 70° C. for 5 hours, brought topH 8 with aqueous sodium hydroxide solution and stirred at 70° C. for 1further hour and the pigment is isolated and dried at 80° C. Theβ-crystal modification of the linear trans-quinacridone with outstandingrheological properties is obtained.

The gloss measurement, as the degree of flocculation of the red-violet,fog-free full shade paint coating on film according to Example 1, gave agloss value of 89.5, in contrast with the value of 79 for thenon-prepared comparison.

(b) If 13.6 parts of the additive obtained according to Example La areemployed as the additive and the procedure is otherwise as described inExample 4a, a red-violet pigment with comparable properties is obtained.

Gloss value: 91.

EXAMPLE 5

A solution of 2.7 parts of the additive obtained according to Example Kand 8.1 parts of ethanol is added to 100 parts of a 6% aqueous-alcoholicsuspension (ethanol content 10%) of the β-crystal modification of C.I.Pigment Violet 19 (73900) at room temperature, with stirring, and themixture is stirred at room temperature for 12 hours. It is then broughtto pH 9.5 with dilute sodium hydroxide solution, subsequently stirredfor 3 hours and filtered with suction and the residue is washed withwater and dried.

The fog-free red-violet full shade paint coating has outstanding gloss.The gloss measurement on film according to Example 1 shows a value of90.5.

EXAMPLE 6

20.4 parts of the solution, consisting of 6.8 parts of a 22% additivesolution (according to Example K) and 13.6 parts of isobutanol, is addeddropwise at 50° C. in the course of 30 minutes to 200 parts of anaqueous-isobutanolic quinacridone suspension (isobutanol content 30%,pigment content 8.8% of quinacridone mixed crystals consisting of 3parts of 2,9-dimethylquinacridone and 1 part of unsubstitutedquinacridone in the lattice of the 2,9-dimethylquinacridone). Themixture is then stirred for 3 hours at 50° C. and then brought to pH 8.5with dilute sodium hydroxide solution and stirred for 2 hours at 50° C.The isobutanol is then distilled off with steam and the pigment isfiltered off, washed with water and dried.

The pigment, a brilliant magenta, exhibits a highly transparent,rheologically almost perfect coating in the alkyd/melamine resin paintsystem, in acrylic/melamine resin paint systems and in TSA-NAD systems.

    ______________________________________                                        Gloss value measured as in Example 1:                                                                 80.5                                                  Non-prepared comparison:                                                                              49                                                    ______________________________________                                    

EXAMPLE 7

A solution of 10.76 parts of the additive obtained according to ExampleI and 22 parts of 100% isobutanol is added to 1,000 parts of anaqueous-isobutanol pigment suspension (isobutanol content 40%, pigmentcontent 6%) of the γ-crystal modification of C.I. Pigment Violet 19 atthe boiling point and the mixture is then stirred at the boiling pointfor 3 hours. It is then brought to pH 7.5 with dilute sodium hydroxidesolution and stirred for a further 2 hours, the isobutanol is distilledoff with steam and the pigment is filtered off, washed with water anddried. 62 parts of a bluish-tinged red pigment powder are obtained.

Gloss measurement on film as described in Example 1 gave a gloss valueof 88.

EXAMPLE 8

A solution of 80 parts of additive solution (22%) (prepared according toExample I) and 160 parts of 100% isobutanol is added in the course of 30minutes at 50° C. with stirring to 2,000 parts of pigment suspension(isobutanol content 50%) which contains 176 parts of a solid solution of2,9-dimethylquinaoridone and unsubstituted quinacridone in a 9:1 ratio.The mixture is then stirred for 3 hours at the boiling point, thenbrought to pH 8-8.5 with dilute sodium hydroxide solution and boiled fora further 2 hours. Subsequently, the isobutanol is distilled off withsteam, and the pigment is filtered off, washed with water and dried at80° C. The magenta pigment obtained in a yield of 98.5% shows in"TSA-NAD" a transparent, fog-free full shade paint coating of high glossand good viscosity.

    ______________________________________                                        Gloss measurement according to Example 1:                                                              78.3                                                 Untreated comparison:    42.7                                                 ______________________________________                                    

EXAMPLE9

125 parts of the 3.6% additive solution, prepared according to ExampleH, are added at 80° C. with stirring to 500 parts of anaqueousisobutanolic pigment suspension (isobutanol content 35%, pigmentcontent 7.5% of a pigment mixture of 8 parts of unsubstitutedquinacridone and 1 part of 2,9-di-N-methyl-carbamoylquinacridone), andthe mixture is boiled for 4 hours. The isobutanol is then distilled offand the pigment is isolated.

    ______________________________________                                        Gloss value of the bluish-tinged red full shade                                                         81.2                                                paint coating according to Example 1:                                         Non-prepared comparison:  28                                                  ______________________________________                                    

EXAMPLE 10

Following the procedure as described in Example 9 but employing, inplace of the additive used there, 25 parts of the additive obtainedaccording to Example M and diluted with 25 parts of diethylene glycolmonoethyl ether, a comparable result is obtained.

EXAMPLE 11

22.5 parts of a solution of a 20% additive, which was obtained accordingto Example D and by subsequent transfer into the propionic acid solutionaccording to Example I, mixed with 45 parts of ethyl alcohol, are addeddropwise at room temperature in the course of 2 hours to 500 parts of anaqueous-alcoholic pigment suspension (ethanol content 40%) whichcontains a pigment consisting of 8 parts of unsubstituted quinacridoneand 1 part of 4,11-difluoroquinacridone. The mixture is then stirred for16 hours at 25°-30° C., then brought to pH 8.5 with dilute sodiumhydroxide solution, heated to the boil and boiled for 2 hours. The ethylalcohol is then distilled off, the pigment is filtered off, washed withwater until free of salt and dried. This give 48 parts of a scarlet-redpigment powder. The gloss measurement on film, as described in Example1, gave a gloss value of 85. The non-prepared comparison . . . (sic) agloss value of 41.

EXAMPLE 12

500 parts of a moist crude quinacridone mixture (solids content 18.5%)of 70% of dimethylquinacridone and 30% of unsubstituted quinacridone aresuspended in 1,000 parts of isobutanol and stirred for 30 minutes at 50°C. 45 parts of 21.8% additive (prepared according to Example Lc),diluted with 90 parts of isobutanol, are then added in the course of 20minutes. Subsequently, the mixture is heated to the boil and boiled for5 hours under reflux, about 200 parts of the aqueous phase of theazetrope (isobutanol content about 8-9%) being separated off. Thepropionic acid is then neutralized with dilute sodium hydroxidesolution, boiling is continued for 2 hours, the isobutanol is distilledoff with steam and the pigment is filtered off. The pigment which hasbeen filtered off is washed with water until free of salt and dried.

The pigment, a brilliant magenta, exhibits a transparent, rheologicallyalmost perfect paint coating in the abovementioned paint systems.

    ______________________________________                                        Gloss value measured as in Example 1:                                                                 82                                                    Non-prepared comparison:                                                                              53                                                    ______________________________________                                    

EXAMPLE 13

20.4 parts of a solution, consisting of 6.8 parts of 22% additivesolution (according to Example Lb) and 13.6 parts of isobutanol areadded dropwise at 50° C. in the course of 30 minutes to 200 parts of anaqueous-isobutanolic quinacridone suspension (isobutanol content 30%,pigment content 7.5% of quinacridone mixture consisting of 2 parts of2,9-dimethylquinacridone and 8 parts of unsubstituted quinacridone). Themixture is then stirred for 3 hours at 50° C. and subsequently broughtto pH 8.5 with dilute sodium hydroxide solution and stirred for 2 hoursat 50° C. The isobutanol is then distilled off with steam, and thepigment is filtered off, washed with water and dried. The pigment, abrilliant bluish-tinged red, exhibits a transparent perfect paintcoating in the alkyd/melamine resin paint system, in acrylic/melamineresin paint systems and in TSA-NAD systems.

    ______________________________________                                        Gloss value measured as in Example 1:                                                                 83                                                    Non-prepared comparison:                                                                              53                                                    ______________________________________                                    

EXAMPLE 14

26.5 parts of a solution, consisting of 6.5 parts of 22% additivesolution (according to Example 9) and 20 parts of isobutanol are addeddropwise at 50° C. in the course of 30 minutes to 200 parts of anaqueous-isobutanolic quinacridone suspension (isobutanol content 30%,pigment content 8% of quinacridone consisting of 1 part of2,9-dimethoxyquinacridone and 9 parts of unsubstituted quinacridone).The mixture is then stirred for 5 hours at 75° C. and subsequentlybrought to pH 8.5 with dilute sodium hydroxide solution and stirred for2 hours at 75° C. The isobutanol is then distilled off with steam, andthe pigment is filtered off, washed with water and dried. The pigment, abrilliant, deeply bluish-tinged red, exhibits a transparent perfectpaint coating in the alky/melamine resin paint system, inacrylic/melamine resin paint systems and in TSA-NAD systems.

    ______________________________________                                        Gloss value measured as in Example 1:                                                                 85                                                    Non-prepared comparison:                                                                              43                                                    ______________________________________                                    

EXAMPLE A

31.5 parts of a 50% solution of a polyisocyanate with the idealizedstructure of the following formula ##STR3## in which R denotes thetolylene radical, 31.5 parts of ethylglycol acetate and 0.04 parts ofdibutyl-tin dilaurate are placed into a stirred vessel and warmed to 50°C. 19.1 parts of a polyester of 1 mole of decanol and 7 moles ofε-caprolactone, dissolved in 19.1 parts of ethylbenzene, are addedrapidly and the mixture is stirred at 80° C. for 1 hour. The NCO contentis thereby reduced from 2.4% at the start of the first part reaction to1.6%.

8 parts of a polyethylene glycol (average molecular weight 1,000) and3.75 parts of N-(3-aminopropyl)-imidazole are dissolved in 73.5 parts ofxylene at 50° C. in a second reaction vessel. The reaction product fromthe first reaction stage is added dropwise in the course of 30 minutesand the batch is stirred at 80° C. for a further 2 hours. An almostclear, colorless, low-viscosity product with a solids content of 25%,the IR spectrum of which no longer shows NCO band, is obtained. Averagemolecular weight of the solid: 6,300.

EXAMPLE B

If in Example A the 1-(3-aminopropyl)-imidazole, employed there, isreplaced by the equivalent amount of 1-(3-hydroxypropyl)-imidazole, acolorless, likewise low-viscosity product having a solids content ofabout 25% and no longer showing an NCO band in the IR spectrum isobtained in an otherwise identical procedure.

Average molecular weight of the solid: 6,200.

EXAMPLE C

If the procedure as described in Example A is followed but, instead of1-(3-aminopropyl)-imidazole, the equivalent amount of4-(3-aminopropyl)-morpholine is employed, a polymeric, likewiselow-viscosity product, in the IR spectrum of which an NCO band is nolonger detectable, is obtained.

EXAMPLE D

If in Example A the polyethylene glycol employed there is replaced by apolyethylene glycol of an average molecular weight of 600, a comparableproduct is obtained in otherwise the same procedure.

EXAMPLE E

10 parts of diglycol dimethyl ether, 24 parts of a 60% solution of apolyisocyanate, the idealized structure of which is given in Example Aand in which, in the indicated formula IV, R represents the toluyleneand hexamethylene radical in the ratio 3:2, and 0.03 parts ofdibutyl-tin dilaurate are placed into a reaction vessel and warmed to50° C. 19.1 parts of a polyester of 1 mole of decanol and 7 moles ofε-caprolactone in 19.1 parts of diglycol dimethyl ether are addeddropwise in the course of 10 minutes. After a reaction time of 2 hoursat 80° C., the NCO content drops from 3.45% at the start of the reactionto 2.3%. 8 parts of a polyethylene glycol (average molecular weight1,000) and 3.75 parts of N-(3-aminopropyl)-imidazole are dissolved in28.25 parts of diglycol dimethyl ether in a second reaction vessel. Thereaction product of the first reaction stage is added to this solutionat 50° C. in the course of 30 minutes and the batch is stirred at 80° C.for a further 2 hours. An almost clear, colorless product with good flowproperties and a solids content of 36.5%, the IR spectrum of which nolonger shows NCO groups, is obtained.

Average molecular weight of the solid: 5,100.

EXAMPLE F

Proceeding as described in Example E but employing, in place of thepolyethylene glycol used there, the equivalent amount of polyethyleneglycol of average molecular weight 1500, a polymeric product no longershowing any NCO bands is likewise obtained.

EXAMPLE G

31.5 parts of a 50% solution in butyl acetate of a polyisocyanurate ofthe formula (IV) (see Example A), in which R represents the toluyleneradical, 31.5 parts of xylene and 0.04 part of dibutyl-tin dilaurate areplaced into a stirred vessel and warmed to 40°-50° C. 19.1 parts of apolyester of 1 mole of decanol and 7 moles of ε-caprolactone, dissolvedin 19.1 parts of xylene, are then added and, for the addition reaction,the mixture is stirred at 40°-50° C.

After the NCO content has decreased by about 25%, 8 parts of apolyethylene glycol (average molecular weight 1000) are added and, afterabout 50% in total have been converted, 3.75 parts ofN-(3-aminopropyl)-imidazole dissolved in 41.4 parts of xylene are addedand the mixture is stirred at 60° C. until NCO groups are no longerdetectable. A viscous, pale amber-colored liquid is obtained.

Solids content about 30%.

EXAMPLE H

100 parts of additive (prepared according to Example G) are evaporatedto dryness in vacuo. The remaining resin is dissolved in 800 parts ofisobutanol.

EXAMPLE I

50 parts of water and 250 parts of propionic acid are added withstirring to 200 parts of the additive obtained according to Example A.With stirring, a solvent/water mixture is distilled off in vacuo at40°-60° C., until xylene is no longer detectable in the bottoms. Thisgives a 22% solution of the additive in propionic acid.

EXAMPLE K

50 parts of water and 275 parts of propionic acid are added withstirring to 200 parts of the 30% additive (prepared according to ExampleG). An azeotrope of xylene, butyl acetate, propionic acid and water isthen distilled off in vacuo (15-20 mm Hg) at 40°-60° C. with stirring,until xylene is no longer detectable in the distillation bottoms. Thisgives an about 20-25% solution of the additive of (sic) propionic acid.

EXAMPLES La-d

Following the procedure as described in Example I but employing 200parts of each of the additives prepared according to Examples B, C, Dand F, the corresponding propionic acid solutions of the additives areobtained:

(a) Propionic acid solution of Additive F

(b) Propionic acid solution of Additive B

(c) Propionic acid solution of Additive C

(d) Propionic acid solution of Additive D

EXAMPLE M

380 parts of diethylene glycol monoethyl ether and 20 parts of water areadded with stirring to 200 parts of the additive (30%) (preparedaccording to Example G). Xylene, butyl acetate and water are thendistilled off in vacuo (about 70 mm Hg) with stirring, until xylene isno longer detectable in the bottoms. This gives an about 15% solution ofthe additive in diethylene glycol monoethyl ether.

We claim:
 1. A powdered pigment which contains at least 5% ofunsubstituted quinacridone and has improved rheological properties foruse in a paint system on an alkyd/melamine, acrylic/melamine,acrylate/isocyanate or polyester/isocyanate basis both of a conventionalnature and of a modern nature of the "high solids" type, into which--asappropriate before, during or after finishing--1 to 20% by weight of theactive substance of a paint additive prepared by reactingpolyisocyanurates which still carry free isocyanate groups and are basedon tolylene diisocyanate, hexamethylenediisocyanate or mixtures thereof,with (1) aliphatic mono- or poly-(hydroxycarboxylic acid)C₁ -C₂₀ -alkylesters (degree of polymerization 2-50), (2) polyethylene glycols(molecular weight 500-1,500) and (3) 5- or 6-membered, saturated orunsaturated heterocyclic compounds which contain at least 1 nitrogenatom in the ring and contain reactive amino or hydroxy-C₁ -C₆ -alkylgroups, until isocyanate groups are no longer detectable, has/have beenapplied.
 2. A process for the preparation of a powdered pigment whichcontains at least 5% of unsubstituted quinacridone and has improvedrheological properties for use in a paint system on an alkyd/melamine,acrylic/melamine, acrylate/isocyanate or polyester/isocyanate basis bothof a conventional nature and of a modern nature of the "high solids"type, which comprises treating the base pigment--as appropriate before,during or after finishing --with 1 to 20% by weight of the activesubstance of a paint additive said paint additive being prepared byreacting polyisocyanurates based on tolylene diisocyanate, hexamethylenediisocyanate or mixtures thereof with (1) aliphatic mono- orpoly-(hydroxycarbocylic acid) C₁ -C₂₀ -alkyl esters (degree ofpolymerization 2-50), (2) polyethylene glycols (molecular weight500-1,500) and (3) 5- or 6-membered, saturated or unsaturatedheterocyclic compounds which contain at least 1 nitrogen atom in thering and still carry reactive amino or hydroxy-C₁ -C₆ -alkyl groups,until isocyanate groups are no longer detectable.
 3. The process asclaimed in claim 2, wherein the active substance of the paint additiveis prepared as set forth in claim 2 and, when used in said process, isdissolved in organic solvent which is at least partially water-miscible.4. The process as claimed in claim 3, wherein said active substance ofthe paint additive, when used in said process, is dissolved in analiphatic alcohol of 1-6 carbon atoms, glycol, glycol ether, glycolester, ketone of the formula ##STR4## aliphatic carboxylic acid of 1-4carbon atoms, aliphatic carboxylic acid amide of 1-5 carbon atoms orcyclic carboxylic acid amide or a mixture of these solvents.
 5. Theprocess as claimed in claim 3, wherein said active substance of thepaint additive, when used in said process, is dissolved in ethanol,propanol, isobutanol, amyl alcohol, ethylene glycol, diethylene glycol,propylene glycol, a glycol mono-C₁ -C₆ -alkyl ether, a diglycol mono-C₁-C₄ -alkyl ether, diglycol dimethyl ether, ethylglycol acetate,methylglycol acetate, butyldiglycol acetate, acetone, methyl ethylketone, methyl isobutyl ketone, diacetone alcohol, formic acid, aceticacid, propionic acid, dimethylformamide or N-methylpyrrolidone.
 6. Themethod of using the powdered pigment of claim 1 comprising the step ofpigmenting a polymeric material with said pigment.
 7. The method ofusing a powdered pigment of claim 1 comprising the step of coloring apaint system with said pigment.
 8. A powdered pigment which contains atleast 5% of unsubstituted quinacridone and has improved rheologicalproperties for use in an alkyd/melamine, acrylic/melamine,acrylate/isocyanate or polyester/isocyanate paint system, said powderedpigment having been treated--before, during or after finishing--with theeffective ingredient of a paint additive prepared by reacting freeisocyanate-containing polyisocyanurates, based on toluylenediisocyanate, hexamethylene diisocyanate or mixtures thereof, with(1)aliphatic mono- or poly-(hydroxycarboxylic acid) C₁ -C₂₀ -alkyl ester,having a degree of polymerization of 2-50; (2) a polyethylene glycolhaving a molecular weight of 500-1500; and (3) a 5- or 6-membered,saturated or unsaturated heterocyclic compound containing at least 1nitrogen atom in the ring and containing a reactive amino or hydroxy-C₁-C₆ -alkyl group;the reaction with the free isocycanate-containingpolyisocyanates being continued until free isocyanate groups are nolonger detectible.